1. Field of the invention
The present invention relates to an optical recording carrier, and a recording-reading apparatus, and a recording-reading process, employing the same. More particularly, it is concerned with an optical recording carrier that records and/or reads information by irradiation with light, and a recording-reading apparatus, and a recording-reading process, employing the same.
2. Related Background Art
Conventionally, the optical recording carrier is known to include optical magnetic discs, optical discs, optical cards, thin-shaped optical discs enclosed with card-like cases, and so forth. In instances in which the optical recording carrier is carried, however, since the optical cards or the thin-shaped optical discs enclosed with card-like cases (hereinafter "card discs"), for example, are so designed that they can be used by being carried by users, it may frequently occur that the optical cards or card discs are deformed by external force when carried, particularly when carried by being put in a purse or the like, and thus the flatness at the time of the production of the optical cards or card discs can not be maintained. The optical discs or the optical magnetic discs are also liable to be deformed when carried.
Whereas, in general, a beam of light irradiated for carrying out recording and/or reading information on a recording layer of the optical recording carrier is required to be made vertically incident on the recording layer. More specifically, if the beam of light is obliquely incident on the recording layer, the spot is given in an elipsoidal shape, so that it is liable that no pit is formed precisely on the recording layer, the information in an adjacent track also is detected to cause the crosstalk, or the return light of the beam of light reflected on the recording layer is not incident on the light-pickup lens to make it impossible to reproduce the information. For this reason, as a means for correcting the deformation such as bend or twist of the optical recording carrier, Japanese Utility Model Unexamined Publication No. 183954/1985 discloses an example in which the vicinity of the part of an optical disc on which part a laser beam flux is reflected is interposed between facing rollers in the form of a sandwich to correct the deformation. However, in the instance of a disc rotating at a high speed, it is liable that no stable rotation can be attained as the disc is interposed between the rollers and also the disc is slightly vibrated as the deformed part comes into contact with the rollers. More specifically, because of the continual change in a focal plane owing to the slight vibration, the autofocusing of pickup can not be followed to make it even impossible to carry out the recording and/or reading.
Namely, as will be seen in the above prior art, no sufficient correction can be achieved against the various types of deformation such as bend, curve and twist of the optical recording carrier if measures are taken only from the aspect of the apparatus.
Moreover, in conventional optical recording carriers, no means for correcting the deformation is taken into account on the part of the optical recording carrier, because they comprise, for example as shown in FIG. 6, a first light-transmissive resin substrate constituting a substrate 1 of the optical recording carrier, an optical recording medium layer 3 that performs the recording by light energy, a second resin substrate corresponding to a protective layer 2 for protecting said optical recording medium layer, and an adhesive layer 8 for adhering said resin substrate. Accordingly, it has been difficult to perform a stable recording and/or reading on the deformed optical recording carrier.